1. Field of the Invention
This invention relates to the field of data transmission systems, and particularly data transmission systems employing networking equipment for transmission of digital information in the form of facsimile transmission to various communications equipment.
2. Description of the Prior Art
Facsimile (fax) messages, in modern-day systems, are oftentimes stored and transmitted in the form of email messages. The originating flax machine typically transmits a fax message through Public Switching Telephone Network (PSTN) communications links to a router device, known as an on-ramp gateway router. A router is a device which selects a path that information can take through a packet switching network environment. This requires the router to have an understanding of the network and how to determine the best route for the path. The on-ramp gateway router transforms the fax message contained in an email message into a Tagged Image File Format (TIFF) file and sends the latter as an email message to another router, known as an off-ramp gateway router (sometimes referred to as an xe2x80x98edge routerxe2x80x99, an edge router is a router having telephony equipment and being coupled on one side to a mail server and on the other side to various communications devices, such as tax machines, through PSTN communications links, accordingly, edge routers are capable of making phone calls). An edge router transforms the email message containing fax information into a tax message, which may be in the form of a TIFF file, for transmission thereof, through PSTN communications links, to a final destination, commonly a receiving fax machine or a device capable of receiving fax information.
This process is not restricted to fax messages. Indeed, any email message can be transformed by the edge router into a fax message and transmitted through PSTN to a destination fax machine. The original email message need not have been produced by a fax machine but could, for example, have come from a Personal Computer (PC) or a modem device.
At present, there are several limitations associated with the part of this process which involves the edge router. An example of an edge router is the AS5300 model (a router device manufactured by Cisco Systems, Inc. of San Jose, Calif.), which has no secondary storage space, such as a hard disk or other known mass storage into which the entire email message or multiple copies thereof can be stored. Storage of the email message allows for ease of reconstruction of the originally-transmitted email or fax message, which is transmitted in packet form. This is perhaps better understood with a brief discussion of the transmission of fax information via email messages.
Email messages are transmitted to router devices through the Internet using an Internet Protocol (IP) standard. Similarly, fax contents of an email message is transmitted through the Internet in packet form. An edge router, which receives the email message, can either send the parsed fax information through the Internet again or it can send it through other communications protocol, such as the PSTN, to receiving fax device(s). Information and therefore email messages travel through the Internet in the form of packets. That is, the message is apportioned into various pieces, referred to as packets, at its originating site and each packet is then sent to the router device separately. Packets belonging to a particular email message are collected by the receiving edge router and appended together in the order in which they were sent to form the originally-transmitted email message. The fax information that is contained in the email message is similarly apportioned into packets prior to transmission thereof to the router. The latter then parses the fax information to form the originally-transmitted fax information and sends the same to fax receiving device(s).
With respect to routers that do not include secondary storage space (such as the Cisco router referred to earlier), there is commonly volatile memory, such as random access memory (RAM), made available for storing one or a few packets of fax information. One of the reasons for the desire to eliminate hard disk or secondary storage space from routers is to reduce the size of the router thereby reducing costs of manufacturing. This discussed at length in a U.S. patent application Ser. No. 09/227,115, entitled xe2x80x9cFAX BROADCAST FROM A SINGLE COPY OF DATAxe2x80x9d, filed on Jan. 8, 1999, the inventors of which are Neil Joffe and Greg Mercurio and the disclosure of which is herein incorporated by reference in its entirety. Another reason for eliminating hard disk in routers is due to the unreliability associated with hard disks in light of the use of mechanical parts in, for example, present-day hard disks. As can be appreciated, mechanical parts generally become defective faster than electrical parts, which is, in part, the cause for the unreliability associated with hard disks.
Accordingly, at any given time, a router device that does not include a secondary storage space and which receives email message can process only a limited number of packets of the email message given the limited amount of memory or storage space contained therein. This limited memory or lack of a secondary memory provides advantages such as a smaller router size, less expensive manufacturing costs and additional reliability as earlier discussed. More details of such routers is described in the U.S. patent application referred to hereinabove.
Once a packet of the message has been processed and transmitted by the router, it is removed or deleted from memory in order to allow available storage space for the next in-coming packet.
Some messages require multiple transmission passes before they are adequately parsed. This poses a problem where transmitted messages cannot be stored in secondary storage. That is, by the time the last packet of the message is processed, the first packet may have been removed from memory and thus no longer available for processing.
For example, assuming that the edge router is transmitting a message consisting of 10 pages of fax contents and further assuming that for some reason, such as malfunction of the receiving fax machine, the fax transmission fails at page 5 there will be no history of transmission maintained in the router""s memory. Thus, rather than sending pages 5-10, the entire message, starting from page 1, must be transmitted one more time.
An example of a prior art network system is shown in FIG. 1 where a mail server 10 is in communication with an array of edge routers having an xe2x80x98nxe2x80x99 number of edge routers.
The mail server 10 sends two messages, 12 and 14, to the first router 18 and another message 22 to the router 20. In the case of failure to successfully send the message(s) to communications device recipients (not shown) that are coupled to, for example, router 18, the router 18 sends an error, message 16 to the mail server, which, in turn, must again request re-transmission of the original message and re-sends the same back to the router 18. This is not only inefficient but it is also expensive in that the message is transmitted in its entirety and adds further PSTN connection time.
The problem with prior art systems is that the address of the original message is an alias for an array of routers serving the local area. The mail server may send the message to a router other than the original router that was used to send the message initially. This is a problem in that because there is no history associated with the message, during re-transmission of the message, it is a requirement for the message to be processed by the same router that was initially used to process the message during the first transmission try.
There are further limitations of the present method of data transfer when more than one recipient fax machine is available. One such limitation is having different speeds associated with different fax machines (or recipients). In order to have proper modem transmission, the router must maintain several fax pages in advance of the fastest recipient in its memory. This is in addition to maintaining the fax pages not yet transmitted to the slowest fax recipient. There is therefore potentially an unbounded-memory problem presented where some fax recipients would have to be dropped in order to keep the memory space within bounds (prevent memory overrun).
Another limitation has to do with transmission of data to multiple recipients. In the event transmission is successful with some recipients and fails with others, there is no way of knowing which one of the recipients has successfully received the message thereby requiring the message to be transmitted to all of the recipients at least one more time.
The need therefore arises for a fax-over-email network system employed in the Internet environment for transmission of fax messages to one or more fax recipients while overcoming the foregoing, limitations as detailed below in the preferred embodiment(s).
Briefly, an embodiment of the present invention includes an email communication system employed in a packet switching network environment for transmission of an email message including at least one fax message for use by fax recipient(s), through the packet switching network environment, includes a network device for communication with one or more mail servers. The mail servers are responsive to an email message having at least one fax message received from an email user. The network device receives the email message, through a forward connection, from one of the mail servers and converts the received email message into the fax message for transmission thereof to at least one tax recipient. The network device further starts to transmit the email message with context information appended thereto, forming a reverse email message, back to one of the mail servers, wherein the mail server is used to store the reverse email message until the mail server is ready to send the same to the network device thereby avoiding the need for secondary storage within the network device.